Use (the bac-cab rule) to expand this triple product:L = mr x (ω x r)
If r is perpendicular to ω, show that you obtain the elementary formula, angular momentum = mvr.
(The bold letters are vectors.)
A X (B X C) = (A[itex]\cdot[/itex]C)B - (A[itex]\cdot[/itex]B)C
The Attempt at a Solution
Well, simply doing the bac-cab rule, I get
(mr [itex]\cdot[/itex]ω)r - (mr [itex]\cdot[/itex]r)ω
Which isn't even close to the answer in the book, which is:
No idea how they got that.
Even if I distribute the r, they don't have it distributed to the ω, and on the right term, they don't distribute the ω. I don't understand.